The design of the Monofoil sailing boat is unique. To open a picture of the Monofoil in a new window with all main components marked click here.

The fuselage (hull) is designed for a pilot and a co-pilot and the underside has a similar profile to that of a flying boat. A rigid wing provides lift and drive and a foil in the water acts as a resisting surface against which the wing reacts. As the craft accelerates, the fuselage starts to lift out. This process starts at speeds of around 20 knots and complete separation from the water is achieved at around the 50 knot mark. At that point, only the foil is in contact with the water.

The foil is a key design breakthrough and as such we are currently unable to disclose exactly how it works. At top speeds it resists a side force of about two tons on a section of only .068 square metres. Consequently it is one of the most highly stressed components on the craft and is also designed to ensure that it is highly resistant to damage caused by collapsing cavitation bubbles.

As Monofoil has aerodynamic controls, one of the priorities has been to make the craft stable at varying speeds.

The height of the fuselage above the water varies from surface-running to an average of about 1.2 metres. This has a number of advantages, the main one being that Monofoil is able to operate in water that is not absolutely flat. In fact the model has flown in conditions with 0.3 to 0.5 metre waves, equivalent to full scale conditions of 2.4 to 4 metres, allowing a much wider range of test areas and greater flexibility in testing conditions.

Unlike many high-speed sailing vessels, Monofoil has the ability to tack and gybe. We believe this is essential to avoid long delays during testing, as a two-tack craft can achieve in the region of ten times as many runs as a one-tack craft. It also makes it a viable proposition to scale up to a larger, long-distance version.

The craft has an operating wind range where the fuselage is airborne from ten knots upto 25 knots. There are a number of wings that are used depending on the weather conditions, although for record runs we will be looking for wind speeds at the top end of this range. Above 25 knots shore side handling becomes the limiting factor and the risk of damage to the craft is increased.